This invention relates to a fluorescence spectrophotometer and in particular to a fluorescence spectrophotometer and a wavelength setting method therefor, which are suitable for setting excitation wavelength and fluorescence wavelength for their optimum wavelengths.
In a fluorescence spectrophotometer the most basic measurement conditions concern the excitation wavelength and the fluorescence wavelength. In order to set them, prior art devices of this kind as disclosed in U.S. Pat. No. 4,330,207 are so constructed that either one of the excitation wavelength and the fluorescence wavelength is fixed, while the other is scanned and set so as to obtain the maximum peak in the spectrum obtained for a sample.
However the prior art techniques described above is based on a thought that the optimum wavelength for a sample is the maximum peak wavelength in the spectrum of the sample. This thought has no inconvenience in the case where the concentration of the sample is high and the sample emits strong fluorescence. However, in the case where the concentration is low or fluorescence emitted by the sample is weak, peaks due to Raman scattering light by the solvent, high order scattering light of the excitation light, etc. are greater than those due to the fluorescence and the optimum wavelength is not always the maximum peak wavelength. Originally a fluorescence spectrophotometer is used often for the purpose of high sensitivity analysis and in many cases the fluorescence of the sample is weak. For this reason, there was a problem that, unless the operator recognizes well that the optimum wavelength is not always the maximum peak wavelength, the function to set automatically the optimum wavelength gives rise rather to erroneous operations for setting the measurement conditions.